Dmedia 0.6 "go time"

This release will focus on the final pieces needed for the player launch (not to mention the first editor release sometime after).

Main areas of focus: 1) add a top level API entry point for "core" functionality (basically everything except importing and transcoding); 2) export this API over dbus and have it run under dmedia-service (existing dmedia-service will be renamed to dmedia-import-service and only deal with imports); 3) add download manager and get dmedia moving files around with HTTP and BitTorrent; 4) finalize the dmedia version 1 schema.